1. Technical Field
The present disclosure relates to a semiconductor integrated circuit having a region capable of switching between supplying power and blocking supply of power individually, and an electronic circuit incorporating the semiconductor integrated circuit.
2. Related Art
While the manufacturing processes for semiconductor integrated circuits, such as System on Chip (SoC), Application-Specific Integrated Circuit (ASIC), Central Processing Unit (CPU), and Graphic Processing Unit (GPU), have resulted in ever greater densities, circuit sizes have continued to increase.
In addition, the semiconductor integrated circuit has built-in various universal interface (I/F) circuits. In particular, the SoC often has built-in not only multiple CPUs and GPUs but also a user logic circuit and multiple universal I/F circuits.
Therefore, in the semiconductor integrated circuit, power consumption tends to increase, and various methods to reduce power consumption have been proposed.
For example, when decreasing use of the circuit, a clock frequency is decreased to a minimum necessary operational frequency for data processing to reduce power consumption. When high-speed processing is required, the clock frequency is increased to execute the process performance. With this operation, the required process performance can be executed, and total power consumption can be decreased.
Further, in order to suppress leak current and further reduce power consumption, another approach proposes a semiconductor integrated circuit that has circuit regions (also called domains) capable of switching between supplying power and blocking power. In this example, inside the semiconductor integrated circuit, there are a circuit region in which the power is supplied (power supply is input) and a circuit region in which the power is not supplied (power supply is blocked). By blocking supply of power to a circuit that does not need to be operated, the leak current is suppressed and the power consumption is decreased.
However, if the above-described countermeasure to reduce the power consumption is performed, the power supply voltage may fluctuate, thus generating noise in the power supply. Noise arises because a resonance frequency determined by the power supply inductance and a power supply capacitance inside the semiconductor integrated circuit matches the spectrum of the operating current, causing the power supply to resonate. The power supply noise is amplified or superimposed due to fluctuation in the voltage level due to the resonance.
In order to solve this problem, for example, JP-2009-094133-A proposes a semiconductor integrated device in which a sensor detects a voltage level applied to the circuit by a sensor, identifies the voltage fluctuation (power supply voltage fluctuation) mode depending on the detection result of the sensor, dynamically changes the power supply impedance based on the determination result, and stops the power supply of a clock when the voltage level detected by the sensor reaches a dangerous level (extremely high voltage level or extremely low voltage level).
Although the above-described device can cope with the fluctuation in the power supply voltage caused by the change in the operational frequency, it is not readily applicable to a semiconductor integrated circuit having the domains to switch between two states of supplying power and blocking power individually. For example, when the sensor detects the voltage of the region in which the power supply is blocked, the detected voltage is identified as at a dangerous level for operation and the supply of the clock is stopped. However, the domain in which the power supply is blocked is not necessary to supply the clock, and thus this control operation is pointless. In addition, if supplying the clock to another domain in which another power supply is input due to this determination, normal operation cannot be performed.
Furthermore, if the sensor detects the voltage level of the domain in which the power supply is not blocked, the domain in which the power supply is blocked increases the fluctuation in the power supply voltage. This state is identified as a dangerous level for operation, supplying the clock is stopped. Therefore, the clock cannot be supplied to the domain in which the operation is needed, which disturbs normal operation.